WMO Reasoning behind Two Sets of “Normals” a.k.a. Two Periods of Base Years for Anomalies

Bob Tisdale - Climate Observations

Most of us are familiar with the World Meteorological Organization (WMO)-recommended 30-year period for “normals”, which are also used as base years against which anomalies are calculated. Most, but not all, climate-related data are referenced to 30-year periods. Presently the “climatological standard normals” period is 1981-2010. These “climatological standard normals” are updated every ten years after we pass another year ending in a zero.  That is, the next period for “climatological standard normals” will be 1991-2020, so the shift to new “climatological standard normals” will take place in a few years. 

View original post 1,365 more words

Leave a comment